Problems with using PLL mode (eg. XTAL1 + PLL1X)
Roger Milne
Posts: 11
I have two propeller 40pin dip's, and have been experimenting with them quite successfully (on a bread-board).
I did kill chip#1 within a few days, and don't know why it died.· It's totally dead to the world.· It was working one night, I killed power and went to bed, and in the morning, it would not communicate with the PC, nor would it download code from an EEPROM.· I wondered if it had anything to do with leaving the prop-plug connected to both the PC and the·propeller chip·(with only the prop-plug and PC powered-up).· That was my only guess as to what went wrong.
Chip #2 has lasted a month or so, and is still kicking.· However, I've never been able to use the PLL clock modes.· I stick with RCFAST since it runs in that mode.
Having written some audio drivers, I started experimenting with the use of crystals and PLL settings again today, to try to boost my speed.
I had a 10Mhz xtal, and attempted to run the chip using "XTAL1 + PLL8X", for 80Mhz.· No go.· Then I found a detail in the datasheet stating that the PLL circuit requires a crystal between 4 and 8 mhz.· Ok, that's why it didn't work.· Could I have done damage by setting it up like that?
Next, I grabbed a 4Mhz crystal, and configured for "XTAL1 + PLL1X", just to see if it would run.· It did, but OMG it was slow.· And not 4Mhz slow...· WAAAYY slower than that.· Mayby 1/4 the speed of running just "XTAL1" with the 4Mhz crystal attached.· I wrote a tiny spin program to toggle the state of a pin forever, and used an oscilloscope to view the output.· What I saw was not a nice symetrical square wave, as I'd expected.· I saw a waveform where each state lasted for what seemed like a random amount of time.· It looked to me like the PLL was having extreme difficulty locking onto the 4Mhz clock.· Some segments of the square wave were 10x longer than others.· I checked the crystal output as well.· It appeared to be perfectly shaped.
Then I started browsing the forums looking for other people who had similar problems...
This thread popped up...
http://forums.parallax.com/showthread.php?p=829126
I am wondering if I have somehow over-voltaged my chip(s).·· I started looking for any source of voltage that could be above 3.0v.· I am powering the board with a +3.0v regulator.· Then, to my horror, I saw that the prop-plug (I made my own, using schematics I found), was outputting 3.4v on some of its' pins.· Technically, that's 0.1v above a spec in the datasheet, in Table 18, "Voltage on all other pins with respect to Vss".· Could this be why I am getting funky PLL behaviour?· Could the voltage on the prop-plug related pins, affect the PLL and clock portions of the chip?
If so, what's the standard work-around for this little difference in voltage?· I am running at 3v because I have an LCD connected, which only runs at 3v.· I am not sure what would happen if I bumped the voltage up on the LCD, and I don't really want to try :-)· At the moment, I don't even know if voltage is the reason I'm having problems, but I fear it could be true.· I am connecting the prop-plug pins directly to the Propeller pins.
Thoughts, anybody???
-- oh, I did try "XTAL1" .. "XTAL3" for each of my crystals, and found no better results than this.
Thanks!
··· Roger
·
I did kill chip#1 within a few days, and don't know why it died.· It's totally dead to the world.· It was working one night, I killed power and went to bed, and in the morning, it would not communicate with the PC, nor would it download code from an EEPROM.· I wondered if it had anything to do with leaving the prop-plug connected to both the PC and the·propeller chip·(with only the prop-plug and PC powered-up).· That was my only guess as to what went wrong.
Chip #2 has lasted a month or so, and is still kicking.· However, I've never been able to use the PLL clock modes.· I stick with RCFAST since it runs in that mode.
Having written some audio drivers, I started experimenting with the use of crystals and PLL settings again today, to try to boost my speed.
I had a 10Mhz xtal, and attempted to run the chip using "XTAL1 + PLL8X", for 80Mhz.· No go.· Then I found a detail in the datasheet stating that the PLL circuit requires a crystal between 4 and 8 mhz.· Ok, that's why it didn't work.· Could I have done damage by setting it up like that?
Next, I grabbed a 4Mhz crystal, and configured for "XTAL1 + PLL1X", just to see if it would run.· It did, but OMG it was slow.· And not 4Mhz slow...· WAAAYY slower than that.· Mayby 1/4 the speed of running just "XTAL1" with the 4Mhz crystal attached.· I wrote a tiny spin program to toggle the state of a pin forever, and used an oscilloscope to view the output.· What I saw was not a nice symetrical square wave, as I'd expected.· I saw a waveform where each state lasted for what seemed like a random amount of time.· It looked to me like the PLL was having extreme difficulty locking onto the 4Mhz clock.· Some segments of the square wave were 10x longer than others.· I checked the crystal output as well.· It appeared to be perfectly shaped.
Then I started browsing the forums looking for other people who had similar problems...
This thread popped up...
http://forums.parallax.com/showthread.php?p=829126
I am wondering if I have somehow over-voltaged my chip(s).·· I started looking for any source of voltage that could be above 3.0v.· I am powering the board with a +3.0v regulator.· Then, to my horror, I saw that the prop-plug (I made my own, using schematics I found), was outputting 3.4v on some of its' pins.· Technically, that's 0.1v above a spec in the datasheet, in Table 18, "Voltage on all other pins with respect to Vss".· Could this be why I am getting funky PLL behaviour?· Could the voltage on the prop-plug related pins, affect the PLL and clock portions of the chip?
If so, what's the standard work-around for this little difference in voltage?· I am running at 3v because I have an LCD connected, which only runs at 3v.· I am not sure what would happen if I bumped the voltage up on the LCD, and I don't really want to try :-)· At the moment, I don't even know if voltage is the reason I'm having problems, but I fear it could be true.· I am connecting the prop-plug pins directly to the Propeller pins.
Thoughts, anybody???
-- oh, I did try "XTAL1" .. "XTAL3" for each of my crystals, and found no better results than this.
Thanks!
··· Roger
·
Comments
Roger,
Did you use _XINFREQ with XTAL??
If you didn't, that may be the problem.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
First of all ... Some bread boards can have very big capacitanse betwen traces That can give XTal its problems.
Next Have you enough Decoplings Caps around Prop?.
With that low voltage that is very important ... Propeller are Variable curent consuming device with very tight time intervals and only Big Decouplings Caps can give it enough Curent/Voltage in that momentary states.
BUT it is posible You have blown PLL already ... sorry in that case
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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.
Sapieha
Leon
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Amateur radio callsign: G1HSM
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April, 2008: when I discovered the answers to all my micro-computational-botherations!
Some of my objects:
MCP3X08/4 ADC Driver - Programmable Schmitt inputs, frequency reading, and more!
Simple Propeller-based Database - Making life easier and more readable for all your EEPROM storage needs.
String Manipulation Library - Don't make strings the bane of the Propeller, bend them to your will!
I have my breadboard setup running since I started with the Prop half a year ago without any problems. I use the 10MHz crystal with these settings:
_CLKMODE = XTAL1 + PLL8X
_XINFREQ = 10_000_000
No problem so far - except that I have to touch each driver demo ;o) ... it's the setup of Hydra as well.
I run it with a lot of different hardware attached. SD card, text LCDs, Graphics LCDs, VGA monitor, Servos, 7 segment displays, LED bars, RAM chip, additional EEPROMs, FRAM .... no problem.
My power supply is a switching power supply 5V, 1,2A and a step down converter to 3.3V. Ok stepdown is a bit more expensive than a 3.3V voltage regulator but I like the idea not to waste the power ;o)
And I did not have a single capacitor in the 3.3V line for a while ... no problem. (Maybe due to the stepdown converter ?)
My USB connector is not the propeller plug, but a different USB to serial converter. The only problem I have with that is that I can't upload programs close to 32kB of size. No problem when USB connected to the PC while Prop is off or vice versa.
The max. Voltage of the propeller is 3.6V, so your 3.4 V comeing from the USB should not be a problem as well.
Maybe you should simply start with a clear breadboard again. Put the propeller to a different place. Corrosion can cause bad connections. Try to follow all the tips mentioned above. Use capacitors, connect all power lines ...
One to thing that I not have mentioned ... Not all bread board have precise hole tags to hold XTal legs .... Use if posible 2 machine pins form old IC holder that You place in bread board and XTal in them.
To have good connection to it.
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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.
Sapieha
I have finished building a proper board for my future prototyping, with proper decoupling, and a 3.3v regulator (I'm pretty sure it's safe to run the LCD at that voltage now).
The "dead" prop is still not working in this setup, so it's looking like it's definitely fried.
The working prop, is still working very slowly, as soon as the PLL is turned on, so I think I've blown it too :-( Hopefully when more 40pin DIP's ship, I'll be able to grab a new one and keep it alive a little longer
Roger
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www.mikronauts.com Please use mikronauts _at_ gmail _dot_ com to contact me off-forum, my PM is almost totally full
Morpheusdual Prop SBC w/ 512KB kit $119.95, Mem+2MB memory IO board kit $89.95, both kits $189.95
Propteus and Proteus for Propeller prototyping 6.250MHz custom Crystals run Propellers at 100MHz
Las - Large model assembler for the Propeller Largos - a feature full nano operating system for the Propeller
I have been naughty to them as well by running one half way beween 3.3 and 5 Volts, so that a CMOS Z80 could bolt on. Again no apparent problems. Loads of people run outside of the 4 - 8MHz bracket and then use pll8X so that the chip gets overclocked with 50/50 mark-space from the fisrt devide by two stage.
It does seem strange that two have died the same way together. Bread boards are not the best for reliable contacts, especially the short ones on DIP chips.
Have you checked the Reset and Brownout pins are not being messed with ?
I have always put the VDD and VSS swap overs right under the chip and either had the caps insid the chip base, or surface mounted between the pin rows, with a electrolytic nearby, not always tants. (Is it because the chip itself cannot supply its own internals without two feeds, or are people trying to use the chip as a set of jumper links??). I still don't know why the VSS and VDD pins swap over, it would be so much easier if the just ran straight across.
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Style and grace : Nil point
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Visit some of my articles at Propeller Wiki:
MATH on the propeller propeller.wikispaces.com/MATH
pPropQL: propeller.wikispaces.com/pPropQL
pPropQL020: propeller.wikispaces.com/pPropQL020
OMU for the pPropQL/020 propeller.wikispaces.com/OMU
From now on I shall rotate every chip I see in a base, in the interests of sciencetific research.
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Style and grace : Nil point
Post Edited (Toby Seckshund) : 11/1/2009 11:40:45 AM GMT
I'm just waiting for more 40pin DIP's to hit the market now, while making due with 16Mhz from a crystal I scavenged from an old board... It's a bit of a boost from RCFAST, but not much...
I cannot pull-off any tricks with over-clocking the PLL since the clocking goes all goofy as soon as the PLL turns on :-(
I did not bother to attach the LCD for the 3.3v tests on the new soldered board. No peripherals, just power, crystal, and decoupling caps. I think this chip has been affected by whatever I was doing wrong, as well.
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www.mikronauts.com Please use mikronauts _at_ gmail _dot_ com to contact me off-forum, my PM is almost totally full
Morpheusdual Prop SBC w/ 512KB kit $119.95, Mem+2MB memory IO board kit $89.95, both kits $189.95
Propteus and Proteus for Propeller prototyping 6.250MHz custom Crystals run Propellers at 100MHz
Las - Large model assembler for the Propeller Largos - a feature full nano operating system for the Propeller